Nowadays, animal hairs focus the spotlight of attention upon the use as a high functional material in the various fields in addition to their rightful use for clothing. For example, the animal hairs have been employed as a trapping agent for heavy metals, an additive for cosmetic and food, a hair tonic, an improver for clothing, an antithrombotic and the like. More extensive uses of the animal hairs have been expected.
For the aforementioned uses as the functional material, fibriform animal hairs must be subjected to pulverization or solubilization because they are unsuitable in themselves.
As a process for pulverizing the fibriform animal hairs, a mechanical pulverization method of the animal hairs themselves, a pulverization method of the pretreated animal hairs with reducing agent, a pulverization method of the frozen animal hairs and the like are exemplified. In these methods, however, a large-scale pulverization apparatus is necessary, sizes of the particulate animal hairs prepared are restricted and complete pulverization of the animal hairs is extremely difficult.
As a process for solubilizing the fibriform animal hairs, the following methods of from (i) to (iii) are exemplified:
(i) A method of extracting protein components after solubilizing the animal hairs by cutting disulfide bond thereof with reducing agent. PA0 (ii) A method of solubilizing the pretreated animal hairs with oxidizing agent in an alkaline solution. PA0 (iii) A method of solubilizing the animal hairs by introducing a hydrophilic group thereinto.
As regards the method (i), use of a solubilizing agent and fairly long solubilization time are necessary because of low solubility of the animal hairs and not only long time is necessary to separate protein gel obtained by dialysis or gel filtration under acidic condition from aqueous phase but also a conservative problem that thiol group of the separated protein gel is reoxidized is brought about because hydrophilicity of the protein gel is considerably high. Concerning the method (ii), it takes long time to solubilize the animal hairs and not only considerable amounts of insoluble animal hairs remain but also long time is necessary to extract the protein. With respect to the method (iii), although solubilization time is relatively short, denaturation of the obtained protein comes into question because said protein is chemically modified by hydrophilic groups.
In connection with the process for solubilizing the animal hairs, a recovery method of the solubilized product of the animal hairs, becomes a subject of discussion. As the recovering method of the solubilized product of the animal hairs, the following methods of (a) and (b) are suggested:
(a) A method of recovering the solubilized product as a gel by adding a volatile inorganic acid such as hydrochloric acid, nitric acid, and the like to the solution of the solubilized product of the animal hairs.
(b) A method of recovering the solubilized product as a water insoluble product by subjecting the solution of the solubilized product of the animal hairs to a crosslinking treatment.
With respect to the method (a), there is a drawback that a filtration treatment becomes very difficult because a filter is blocked by a gelled protein. As regards the method (b), there is a disadvantage that a use of the collected product is excessively restricted because the animal hair protein is chemically modified completely by a crosslinking agent.
Although a flocky precipitate can be obtained in the method (a) when the pH of the solution is lowered by increasing a concentration of the inorganic acid, a color of the precipitate is turned to brown when the precipitate is subjected to a drying treatment in an insufficiently dehydrated state because dehydration efficiency of the precipitate is extremely low, said low efficiency of the dehydration being attributable to the occluded water within the precipitate.
In addition to the abovementioned methods, it is known that the gelled protein obtained by the method (a) may be dehydrated by washing said protein with a volatile polar solvent such as alcohol, acetone and the like. However, it is hard to supply the solubilized product of the animal hairs at a low price because a large quantity of the solvent which is relatively expensive must be used and, therefore, it is necessary to utilize an apparatus for recovering the used solvent.